Torque converters are well known in the art. Commonly, torque converters include a damper assembly for improving noise or resonance of the torque converter or components of the torque converter during operation.
An example of a typical constant friction torque converter damper is shown in FIG. 1. As shown, damper 10 includes covers 12 and 14 on either side of flange 16. Torque from piston plate 18 is transmitted to cover plates 12 and 14, typically via a riveted connection. Cover plates 12 and 14 impart torque to compression springs 20 by contact with an edge of a spring window. Energy absorption is often accomplished through friction, sometimes called hysteresis, which includes friction from windup and unwinding of the damper plates. The hysteresis package generally consists of diaphragm (or Belleville) spring 22 which is placed between flange 16 and cover plate 14 to urge flange 16 into contact with cover plate 12. By controlling the amount of force exerted by diaphragm spring 22, the amount of friction torque can also be controlled. However, the amount of friction in this arrangement is constant regardless of the rotational speed of the assembly, whereas it has been found that high friction is desired for reducing resonance in low speed operations, while low friction is desired for reducing resonance in high speed operations. Additionally, in order for spring 22 to operate, it must be included about the entire circumference of the damper flange, and results in a significant quantity of scrap material when stamped during manufacture.
Such a damper arrangement is also described in several patent references, including United States Patent Publication No. 2009/0032364 (MacDonald et al.), which publication is hereby incorporated by reference in its entirety.
Accordingly, there have been attempts to modify or vary the friction in a damper during operation of the torque converter, such as to improve resonance more effectively at high and low rates of rotational speed, instead of constant friction at all rates of speed. Examples include: U.S. Pat. No. 4,640,402 (Hartig et al.), which shows a damper with a manually adjustable hysteresis for reduced tolerance variation; U.S. Pat. No. 4,465,172 (Gatewood), which shows a damper with friction that varies with the windup angle; U.S. Pat. No. 6,681,911 (Kroll et al.), which shows a damper with hysteresis that is adjustable by fluid pressure; and U.S. Pat. No. 4,376,477 (Loizeau), which shows a damper that uses a centrifugally acting element to engage and disengage spring sets. U.S. Pat. No. 4,640,402 (Hartig et al.), U.S. Pat. No. 4,465,172 (Gatewood), U.S. Pat. No. 6,681,911 (Kroll et al.), and U.S. Pat. No. 4,376,477 (Loizeau) are hereby incorporated by reference in their respective entireties.
The use of centrifugal clutches in torque converters is also generally known, however these clutches are known to increase friction with increased rotational speed, although the exact opposite is desired for damper's hysteresis package. Examples can be found in U.S. Pat. No. 4,657,122 (Sakakibara et al.) and U.S. Pat. No. 4,383,596 (Jaeckel). All of these various patents teach complicated assemblies consisting of numerous parts that require significant circumferential or angular space for installation.